Integrating Solar Thermal Energy at the Large Scale

Carlos E. Romero

Director, Energy Research Center

Lehigh University

Bethlehem, Pa 18015, USA

Introducing Renewables to the Grid

• However, there are clear incentives to explore options for combining intermittent renewables, such as CSP with TES with conventional thermal power plants.

Source: Mayes, F., Today in Energy, http://www.eia.gov/todayinenergy detail, Sept., 2014

True Hybrid Power Plants

• Hybridrizing coal, oil and NG with thermal solar energy offers a route to combining renewable energy with stable efficient geneneration assets. It is less expensive than an equivalent stand-alone CSP plant.

• Hybrid models take advantage of economy of installation.

• Hybrid models reduce problema of solar power’s variability.

• Hybrid models can help meet renewable portfolio standards and CO2 reduction goals.

• Hybrid models can reduce fuel consumption, improve overall unit efficiency, boost power generation (at peak loads), reduce pollutant emissions and CO2, extend plant lifespan.

• Potential interface points: • High pressure feedwater – Boost mode • Low pressure feedwater – Fuel saving mode • HP/IP steam – Fuel saving mode and boost mode • Other low enthalpy usage points (air preheat, flue gas reheating, auxiliary steam, CCS, impaired

water treatment, etc.)

True Hybrid Power Plants

•Dissavantages: •Water requirements •Requirement of suitable land close to the existing

termal power plant •Capital investment and additional O&M •Practical issues have limited existing hybrid

projects to about 5% (new plant could be more like 30-40%) R&D Opportunities?

Experience with Hybrid Solar Thermal Plants

• Currently, there are around 15 hybrid solar thermal plants developed or in development, with a total capacity of 460 MW.

• EPRI has been engaged with an 1,100 MW NGCC with 95 MW of solar energy (NV Energy, Nevada), and a 245 MW coal plant with 36 MW of solar energy (Tri State G&T, Escalante, New Mexico).

• Florida Power and Light developed a 75 MW solar plant to supply heat to one of the two 800 MW steam turbines of its gas-fired Martin Power Plant.

• In Palisade, Colorado, Xcel Energy is retrofitting its Cameo Generating Station. The hybrid plant will produce the equivalent of just 1 MW (of the plant’s 49 MW) from solar power.

• In Morocco and Algeria, there is: a 470 MW plant, with the solar system providing 20 MW; and a second project at the 150 MW Hassi R’Mel plant, where the solar contribution to the total output is estimated at ~20 MW.

• In Mexico, there is a new solar-natural gas project (Agua Prieta II), where a CSP plant will contribute 12 MW to a 464 MW combined cycle facility.

• Australian utility CS Energy completed in 2013 adding 44 MW solar thermal add-on to its coal-fired 750 MW Kogan Creek plant in Queensland.

• In Chile, GDF Suez and German renewable energy company Solar Power Group is developing a 5 MW concentrated thermal solar power plant to provide steam to the 150 MW Mejillones coal-fired plant.

Integrating Solar TES with NGCCs in Mexico

Temperature Profiles in HRSG of the Base Case NGCC Model and the Solar Thermal Energy Aided Combined Case NGCC Model

Power Boost Solar Addition

Duct Fuel Saving Solar Addition

NGCC power plant located in Hermosillo, Mexico, equipped with a 150 MW gas turbine and a 93 MW steam Rankine cycle. The Hermosillo area has a standard DNI of 887 Wth/m2 and 8.5 peak sun hours per day, the average annual solar irradiation is approximately 2,752 kWh/ m2.

Integrating Solar TES with NGCCs in Mexico

For the optimal fuel saving case involving 2.27 MWth of solar input, the estimated annual energy cost benefit from the solar collectors would be $0.031 Million USD.

For the optimal benefit case of 0.69 MWth of solar input, the predicted power gain would be 0.297 MWe , there would be no reduction in fuel use and the estimated annual energy cost benefit would be $0.040 Million USD.

Integrating Solar TES with Geothermal PPs in Mexico

Geothermal plant rated at 100 MWe and located at the Cerro Prieto Power Plant, in Mexicali, Baja California, Mexico. Mexicali, Baja California has a standard DNI of 887 Wth/m2 and 8.5 peak sun hours per day, the average annual solar irradiation is approximately 2,752 kWh/m2.

P(x) = 0.0016x2 + 0.2134x + 0.0586 R² = 0.9999

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Total Solar Thermal Energy Input (MWth)

Solar to Electricity Conversion Rate

Power Gain

Integrating Solar TES with Geothermal PPs in Mexico

Comparisons of the estimated financial benefit due to increased power production to the estimated installed costs of the solar collector array were carried out for installed costs per dish from $17,500 to $27,500 USD and annual interest rates from 2 to 5%. The results show, for the range of solar thermal inputs, the break-even cost per dish would be a strong function of annual interest rate.

Opportunities on the Water-Energy Nexus

Opportunities on the Water-Energy Nexus